Botachusmajor, Kim & Boxshall, 2020

Kim, Il-Hoi & Boxshall, Geoff A., 2020, Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata), Megataxa 4 (1), pp. 1-6 : 158-162

Botachusmajor sp. nov.

( Figs. 103–105 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21247 ) , paratypes (intact, 2 ♀♀ and 1 ♂, MNHN-IU-2014-21248) , anddissectedparatype (♀, figured), from Ascidia involuta Heller, 1875 (MNHN-IT-2008-1058 = MNHN P5/ ASC.A/255), Sierra Leone, Iles Banana, R / V “Sea Diver”, depth 28 m, 04 October 1990; 1 ♂ (dissected and figured) from A. involuta , Sierra Leone 04 October 1990, depth 28 m .

Etymology. The specific name is from the Latin major , meaning “larger”, and refers to the body size of the new species.

Descriptionoffemale. Body ( Fig. 103A ) slender, curved ventrally, and distinctly segmented. Bodylength 2.07 mm. Prosome depressed; fourth pedigeroussomite forming brood pouch, about 700×370 μm in lateral view, as long as anterior part of prosome: fifth pedigerous somite completely fused with fourth. Free urosome ( Fig. 103B ) cylindrical, 5-segmented, narrowingposteriorly. Genital somite 102×193 μm, with copulatory pore on ventral surface; 4 abdominalsomites 193×168, 182×125, 116×102, and 45×75 μm, respectively. Anal somite ( Fig. 103C ) with paired tapering posteroventral protuberances densely ornamented with minute spinules on ventral surface; anal operculum large. Caudal ramus ( Fig. 103C ) short, divergent, with ventrodistal extension; armed with 2 claws and 4 setae, ornamented with scattered rows of minute spinules; 2 claws unequal in thickness, thick claw 42 μm long, thin claw 50 μm.

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-I	I-1; I-1; VI, 1	0-0; 1, 2, 2
Leg 2	0-0	1-0	I-1; I-1; VI, 2	0-1; 0-0; 1, I, 3
Leg 3	0-0	1-0	I-0; I-1; V, 2	0-1; 0-0; 1, I, 3
Leg 4	0-0	1-0	I-0; I-1; V, 2	0-0; 0-0; 1, I, 2

Rostrum ( Fig. 103D ) longerthanwide (79×68 μm), narrowing towards rounded distal margin. Antennule ( Fig. 103E ) 158 μmlong, 8-segmented; armatureformula 4, 14, 9+aesthetasc, 4, 3+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; setae crowded and generally long, several setae on proximal segments pinnate; first and second segments each with 1 transverse row of minute spinules. Antenna ( Fig. 103F ) stout, 4-segmented; coxa short and unarmed; basis nearly as long as wide, exopod represented by 1 large pinnate seta and 1 small setule at outer distal corner; ornamented with 2 rows of setules on inner surface; first endopodal segment as long as basis, with 1 small setasubdistally and curved row of small spinules; compound distal endopodal segment about 2.8 times longer than wide (53×19 μm), with spinulose inner surface and setulose distal outer margin; armed with 9 setae plus terminal claw 38 μm long, more than half length of segment.

Labrum ( Fig. 103G ) simple, smooth, with broad posteromedian lobe. Mandible ( Fig. 103H ) with 4 teeth and 1 thin proximal seta on coxal gnathobase, proximalmost tooth bifid; 1 needle-like spinule present between distal second and third teeth; basis with 1 seta at mediodistal corner and scattered rows of minute spinules; exopod 2-segmented and armedwith 3 and 2 setae on first and second segments, respectively, outer distal seta on second segment shorter than other exopodal setae; endopod unsegmented, armedwith 12 setae (4 on anterior surface and 8 on distal and subdistal margins); medial margin of endopod ornamented with row of minute spinules proximally and row of setules distally. Maxillule ( Fig. 103I ) with 8 setae on arthrite, 1 seta and patch of minute spinules on coxal endite, 2 unequal setae on epipodite, and 3 unequal setae on medial margin of basis; exopod with 4 distal setae increasing in length from inner to outer; endopod smaller than exopod, with 3 distal setae increasing from outer to inner. Maxilla ( Fig. 104A ) 5-segmented; syncoxawith 3, 1, 2, and 3 setaeonfirst to fourth endites, respectively, proximal seta on distal endite minute; basis with 3 setae; first to third endopodal segments with 1, 1, and 4 setae, respectively. Maxilliped ( Fig. 104B ) lobate, broadened distally, armedwith 10 setae (8 medial and 2 apical); ornamented with scattered rows of fine spinules.

Leg 1 ( Fig. 104C ) with 3-segmented exopod and 2-segmented endopod. Legs 2–4 ( Fig. 104 D–F) with 3- segmented rami. Coxa of legs 1–4 unarmed. Outer seta on basis large and pinnate in legs 1–3, but small and naked in leg 4. Inner distal spine present on basis of leg 1, 15 μm long, shorter than first endopodal segment. Inner seta on second exopodal segment of legs 3 and 4 small and naked. Armature formula for legs 1–4 as follows:

Leg 5 ( Fig. 104G ) small, consistingof digitiform protopod and exopod; protopod tipped with naked seta (58 μm long); exopodal segment articulated from protopod, 20×9 μm, armed with 1 naked seta (58 μm long) at tip and 1 small subdistal seta (7 μm long).

Descriptionofmale. Body ( Fig. 105A ) 1.64 mm long. Prosome 800 μm long. Fourthpedigerous somite with concave posterodorsal margin ( Fig. 105B ). Fourth pedigerous and urosomites well-sclerotized. Urosome 6-segmented; fifthpedigerous somite 113×264 μm; genital somite ( Fig. 105C ) 123×259 μm, as short as fifth pedigerous somite, withsmall genital operculum ventrally. Abdomen strongly curved ventrally. First abdominal somite ( Fig. 105C ) 216×255 μm, ornamented with 10 tubercles on ventral surface. Anal somite ( Fig. 105D ) lacking posteroventral protuberance. Caudal ramus ( Fig. 105D ) slightly narrowing distally, 45×42 μm, armed with 2 claws plus 4 setae; claws very unequal, one robust, conical, 60 μm long and 27 μm wide, outer distal claw 77 μm long and 8 μm wide; 1 seta inserted into basal part of robust claw (2 dorsal setae missing in Fig. 105D ).

Rostrum ( Fig. 105E ) longer than that of female. Antennule 8-segmented and similartothatof female; armatureformula 4, 12+2 spines, 8+aesthetasc, 4, 3+aesthetasc, 2, 2, and 7+aesthetasc. Antenna, labrum, mandible, maxillule, maxilla, and maxilliped as in female.

Leg 1 also as in female. Legs 2–4 ornamented with large spinules along distal border of first and second endopodal segments ( Fig. 105F, G ). Third endopodal segment of leg 2 armed with 2 spines and 3 setae. Legs 3 and 4 each with large inner seta on second exopodal segment ( Fig. 105G ). First endopodal segment of leg 4 with inner seta.

Leg 5 ( Fig. 105C ) small and consisting of short protopod and exopod; protopod with 1 naked setaon outer distal corner; free exopod rectangular, armed with 2 setae distally (short pinnate inner seta and long naked outer seta). Leg 6 ( Fig. 105C ) represented by 3 setaeon genital operculum, small inner seta pinnate, other 2 longer setae naked.

Remarks. The new species B. major sp. nov. differs from the type species, B. cylindratus , in numerous characters. The major differences are summarised in Table 2, and collectively these are sufficient to justify the establishment of the new species.

Figures

FIGURE 103. Botachus major sp. nov., female. A, habitus, right; B, urosome, ventral; C, anal somite and caudal ramus, right; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule. Scale bars: A, 0.2 mm; B, 0.1 mm; C, E-I, 0.02 mm; D, 0.05 mm.

FIGURE 104. Botachus major sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 3; F, leg 4; G, leg 5. Scale bars: A, B, G, 0.02 mm; C-F, 0.05 mm.

FIGURE 105. Botachus major sp. nov., male. A, habitus, right; B, habitus, without last 2 abdominal somites, dorsal; C, proximal part of urosome showing legs 5 and 6, ventral; D, anal somite and caudal rami, dorsal (stippled circles indicating insertion positions of setae); E, rostrum; F, leg 2; G, leg 4. Scale bars: A, B, 0.2 mm; C, 0.1 mm; D-G, 0.05 mm.